1. Field of the Invention
The present invention relates to a copying apparatus capable of duplex copying, and more particularly to the control of such a copying apparatus for copying two documents different in size or direction on the front face (face) and rear face (back) of copy paper.
2. Prior Art
There have heretofore been proposed many duplex copying apparatus capable of copying images on both surfaces of copy paper to reduce the number of copied sheets, for example, as described in U.S. Pat. No. 3,615,129. The conventional duplex copying apparatus operate to form a copied image of a first original document on the face of copy paper and a copied image of a second original document on the back of the copy paper.
In general, however, the sizes of the first and second documents are not necessarily the same. Where the second document is larger in size than the first document and the first and second documents are copied on the face and back of the copy paper at the same magnification, a copied image of the second document is not properly contained within the frame of the back of the copy paper. When the user of the copying apparatus manually replaces documents, it is possible to select suitable copying magnifications. However, the user often tends to forget to change copying magnifications, and it is troublesome to change such magnifications. Where the copying apparatus is combined with a document feeder which automatically positions documents on a transparent plate of glass serving as a document support, the conventional copying apparatus fails to allow copying magnifications to be changed for each document to be copied.
Likewise, in the event that the first and second documents are positioned on the transparent glass plate in different directions, a copying failure may result in which a copied image of the second document does not fall within the size of the back of the copy paper.